The present invention relates generally to a cored, shirred casing article, method and apparatus for use in automatic stuffing operations. More particularly the invention relates to such an article including means for controlling the deshirring of the casing from the article so as to permit accurate detection of the depletion of casing by the control mechanism of the stuffing apparatus. In its method aspect the invention relates to the use of such an article in detecting the depletion of casing and controlling the termination of a stuffing operation in response to such detection.
Shirred casing articles are commonly used in automatic stuffing operations to improve the rate of producing encased food products. These casing articles contain a relatively long length of casing which has been shirred and compacted to a relatively short length called a "shirred casing stick". For example, a stick less than 20 inches long may contain a continuous length of casing measuring as much as 160 feet or more in length. These sticks are sufficiently coherent so that they can be handled by the mechanical loading apparatus of a stuffing machine.
In a high speed, automatic stuffing operation, such as the production of frankfurters, the entire supply of casing contained in a casing stick is depleted in a matter of less than a minute. Because of the rapidity with which the shirred casing stick stuffed, it is important for the stuffing machine to be able to detect when the supply of casing in a stick is about to become depleted. This allows the machine controls to stop the stuffing operation just prior to the depletion of the casing supply so that a fresh stick can be brought into a stuffing position.
In frankfurter production, a common method of detecting casing depletion is to place the casing stick over the stuffing horn at the start of the stuffing operation, and then bias the stick towards the discharge end of the stuffing horn. This is done by a push rod biased against a ring contacting the trailing end of the casing stick. As casing is stuffed and deshirred from a fore end of the casing stick, the push rod urges the remaining shirred portion of the stick towards the discharge end of the stuffing horn. The position of the push rod, which is positioned against a ring contacting the trailing end of the casing stick, in effect monitors the position of the end of the casing stick. Accordingly the approach of the push rod towards the discharge of the stuffing horn is used to indicate depletion of the casing and to control the termination of the stuffing operation.
While push rods or other similar casing contacting sensors can be relied upon to monitor the end of a conventional casing stick, the advent of cored casing sticks has made it necessary to find other means for indicating the impending depletion of casing.
A cored casing stick has a rigid tubular core disposed within the bore of the casing stick. A shirred casing stick which includes a substantially rigid tubular core offers several advantages over more conventional, uncored sticks. For example, the core provides the casing stick with greater coherency so that the stick is less likely to break during the rigors of automatic handling. Another advantage is that the tubular core can itself function as a disposable stuffing horn which is discarded after a single use. Cored casing sticks can be made to contain greater lengths of casing than uncored sticks, which is important for increasing production in automatic stuffing operations.
Briefly, to make a cored casing stick, a strand of shirred casing, preferably a compacted strand, is pushed over a rigid tubular core. As an alternative, a strand of shirred casing can be compacted directly on to a core. A further alternative is to shirr directly on to a core with or without subsequent compacting. In any event, the inside diameter of the shirred casing strand and the outside diameter of the tubular core are selected so that the inner periphery of the shirred casing strand will contact about the outer periphery of the core, preferably over substantially the full length of the casing strand. Moreover, this contact between the casing strand and tubular core should be sufficient to provide a resistance to relative motion between the strand and the core.
When using a cored casing stick, the tubular core is mounted over a stuffing horn or the stuffing horn can be eliminated and its function assumed by the tubular core. However, regardless of how the cored casing stick is used, the trailing end of the casing strand canhot be pushed along the core towards the stuffing horn discharge as with uncored sticks. This is due to the resistance to relative motion provided by the contact between the core and the casing strand. Accordingly, the conventional push rod arrangement for monitoring the position of the trailing end of the casing strand is inappropriate when using cored casing sticks.
There is still another characteristic of cored casing sticks which makes it difficult for conventional monitors to accurately indicate depletion of casing. In this respect, the resistance to relative motion between casing strand and core tends to decrease towards the ends of the casing strand. Various factors contribute to this.
For example, the inherent resiliency of the shirred casing strand tends to cause it to expand axially. This axial expansion loosens the casing on the core and works to at least partly reduce the resistance to relative motion between the casing strand and core, particularly adjacent to the ends of the casing strand. The material of the core, its surface finish, amount of compaction, etc., are all variables which have a bearing on the resistance to relative motion between the casing strand and core.
For the most part this resistance is sufficient to maintain the unshirred portion of casing strand anchored to the core while casing deshirrs from the casing strand. That is, the magnitude of this resistance is greater than the force required to deshirr casing from the strand. However, as casing deshirrs from the strand, the length of the strand decreases. As the strand length decreases, the resistance to relative motion between a remaining portion of the strand and the core decreases. If a point is reached where this resistance falls below the deshirring force, the entire remaining portion of casing strand will break free and begin to slide axially along the core responsive to the deshirring force. Accordingly, movement of the trailing end the casing strand under these circumstances may not reflect the true amount of casing remaining in the strand. For example, sensors designed to initiate termination of the stuffing operation responsive only to movement of the trailing end of the strand will activate prematurely if the remaining portion of the strand contains a relatively long casing length. That is, stuffing may terminate before all the usable casing has been depleted.
In the present invention movement along the core of the trailing end of the casing is controlled and made predictable so that sensors monitoring the end of a casing can correctly indicate the depletion of the casing. This is accomplished by providing a means carried by the core which engages the casing and controls the movement of the trailing end of the casing so that the depletion of casing can be accurately indicated by sensors monitoring the position of the trailing end of the casing.